PU potting compound improves thermal stability in e-wheelchair motors

Electric wheelchairs are required to operate reliably in demanding real-world scenarios, including situations where drive wheels become obstructed by curbs or uneven terrain. In such cases, electric motors can experience rapid temperature spikes within seconds. A wheelchair manufacturer approached Wevo after conventional potting materials failed to prevent overheating in these conditions.

Working as a development partner, Wevo supported the customer through material selection, processing and scale-up, ultimately delivering a tailored PU potting system designed for both thermal management and electrical insulation in series production.

At the core of the solution is a low-viscosity polyurethane potting compound capable of fully impregnating stator windings. The material enables void-free encapsulation, ensuring consistent electrical insulation while also facilitating efficient heat transfer. By conducting heat away from current-carrying copper conductors to the motor housing, the system reduces localised hot spots and mitigates temperature peaks generated during stall events.

According to Wevo, the optimised PU formulation significantly improved thermal performance, lowering motor temperature profiles below initial design assumptions while maintaining output and efficiency. This also enabled a reassessment of the required material specifications, with target values for thermal conductivity and temperature resistance reduced once the system-level performance had been validated.

Beyond materials, the project highlights the role of application engineering in PU potting. Measurement data generated during development allowed early-stage design modifications, resulting in a more compact, planar motor architecture suited to the tight installation space typical of modern electric wheelchairs. This integration of material and component design was a key factor in achieving both performance and packaging targets.

The work underlines the importance of application-specific formulation in polyurethane potting systems. Rather than selecting materials based solely on datasheet values, the solution was developed through close alignment of material properties, processing behaviour and end-use requirements.
For PU suppliers and processors, the project illustrates how thermally conductive potting compounds can enable improved reliability and miniaturisation in electric drive systems, particularly in mobility applications where space constraints and transient thermal loads are critical design factors.

Photo: an e-wheelchair mounts a kerb © Wevo-Chemie

Wevo-Chemie